• Energy Research

Abstract Oil palm trunk (OPT) an abundant agriculture waste was evaluated as an alternative lignocellulosic biomass resource for bioethanol production. Sulfite-based SPORL pretreatment (Sulfite Pretreatment to Overcome Recalcitrance of Lignocellulose) was applied to the OPT to enhance its enzymatic saccharification. The pretreatment conditions were optimized through a designed experiment within the ranges of temperature 170–190oC, time for 30 min, 2–6% sulfite, and initial H2SO4 concentrations 3–7% (w/w). The overall saccharides (hexoses and pentoses) recovery of SPORL pretreated was 62.5%. SPORL pretreatment removed 38.8% lignin from the OPT as lignosulfonate in the liquor with great potential for co-product development, and 93.9% xylose was dissolved, which were the main reasons why the SPORL pretreatment could enhance the enzymatic hydrolysis of the OPT. The results indicated that over 92% of the cellulose in the pretreated OPT with 7% H2SO4 and 6% Na2SO3 at 190oC was enzymatically hydrolyzed to glucose within 48 h with a cellulase loading of 15 FPU/g cellulose, and overall glucose yield was 66%.

AbstractEthanol production from oil palm frond (OPF) by simultaneous saccharification and Saccharomyces cerevisiae TISTR5048 fermentation was investigated. Solid fraction of OPF (20% TS) was pretreated by 2% H2SO4, 2% NaOH and 2% NaOH in H2O2 presoaking at room temperature for 24hours. Pretreated OPF by presoaking in 2% H2SO4, 2% NaOH and 2% NaOH in H2O2 contained 37%, 42% and 49% of cellulose, respectively. Pretreated OPF was simultaneous saccharification by cellulase enzyme (Cellic CTec2, Novozymes) and sequentially fermentation. Sugar concentration in OPF cellulose hydrolysis of 2% H2SO4, 2% NaOH and 2% NaOH in H2O2 presoaking was 45.72, 55.73 and 56.94g/l, respectively. Ethanol concentration of 2% H2SO4, 2% NaOH and 2% NaOH in H2O2 presoaking was 14.5, 15.0 and 17.2g/L, respectively. 2% NaOH in H2O2 presoaking was the best pretreatment with 82.11% of total solids recovery and containing 49.9% of cellulose with enzyme digestion ability of 37.6%.

Abstract Hydrothermal carbonization aqueous phase (HTC-AP) can be used for methane production by anaerobic digestion (AD). However, it generally had low conversion efficiency due to the formation of complex dissolved organic matters, which depends upon the components of biomass. The present study investigated the characteristics, methane potentials, and recalcitrant chemicals of HTC-AP produced from different combinations of model compounds carbohydrate (α-cellulose, C) and protein (bovine serum albumin, BSA) with mass ratios of 1:0, 0.75:0.25, 0.5:0.5, 0.75:0.25 and 0:1. The methane yields of samples 1:0 (pure C) and 0:1 (pure BSA) were 192 mL/g COD and 187 mL/g COD, respectively, while it was decreased to 105.5 CH4 mL/g COD for sample 0.75:0.25 (C/BSA), indicating more recalcitrant organics were produced with the combination of C and BSA. It was found that the mean MW (209157) of sample 0.75:0.25 was much higher than the other samples (

Abstract Thermotolerant consortia were obtained by heat-shock treatment on seed sludge from palm oil mill. Effect of the initial pH (4.5–6.5) on fermentative hydrogen production palm oil mill effluent (POME) showed the optimum pH at 6.0, with the maximum hydrogen production potential of 702.52 mL/L-POME, production rate of 74.54 mL/L/h. Nutrients optimization was investigated by response surface methodology with central composite design (CCD). The optimum nutrients contained 0.25 g urea/L, 0.02 g Na 2 HPO 4 /L and 0.36 g FeSO 4 ·7H 2 O/L, giving the predicted value of hydrogen production of 1075 mL/L-POME. Validation experiment revealed the actual hydrogen production of 968 mL/L-POME. Studies on the effect of temperature (25–55 °C) revealed that the maximum hydrogen production potential (985.3 mL/L-POME), hydrogen production rate (75.99 mL/L/h) and hydrogen yield (27.09 mL/g COD) were achieved at 55, 45 and 37 °C, respectively. Corresponding microbial community determined by the DGGE profile demonstrated that Clostridium spp. was the dominant species. Clostridium paraputrificum was the only dominant bacterium presented in all temperatures tested, indicating that the strain was thermotolerant.

AbstractThe laboratory-scale UASB reactors were operated at five different hydraulic retention times (HRTs). The various sizes of granules from three different sources: a cassava factory (CS), a seafood factory (SS), and a palm oil mill (PS), having the size range of 1.5-1.7mm, 0.7-1.0mm and 0.1-0.2mm. respectively, were used as inocula for anaerobic digestion of cassava wastewater. For comparison, the first reactor with only granules from its own source (R1, CS) was treated as control. The other two reactors were inoculated with mixed granules from different sources (R2, CS+SS and R3, CS+PS). As HRT decreased from 5 days to 1 day, the organic removal efficiencies decreased from 91.49 to 43.23%, 89.36 to 45.13% and 87.23 to 32.69% for R1, R2 and R3 respectively (or inversely with increasing OLR). In this study selected mathematical models including Monod, Contois, Grau second-order and Modified Stover-Kicannon kinetic models were applied to determine the substrate removal kinetics of UASB reactors. Kinetic parameters were determined through linear regression using experimental data obtained from the steady-state experiments and subsequently used to predict effluent COD. The results showed that Grau second-order and Modified Stover-Kicannon kinetic models were more suitable than the others for predicting the substrate removal for all different sizes of granules. In addition the Upflow Anaerobic Sludge Blanket (UASB) reactor with only granules from a cassava factory gave the best performance.

Abstract Empty fruit bunches (EFB), palm oil mill effluent (POME), sewage chemical sludge and sewage biological sludge were evaluated for methane production under liquid-state anaerobic digestion (L-AD) and solid-state anaerobic digestion (SS-AD). The highest methane yield of 456 mL CH 4 g -1 VS was achieved from co-digestion POME with sewage chemical sludge at a ratio of 99:1 under L-AD. The highest methane yield of 18 mL CH 4 g -1 VS was achieved from co-digestion EFB with sewage chemical sludge at a ratio of 95:5 and EFB with sewage biological sludge at a ratio of 95:5 under SS-AD. An increasing of sewage sludge content of 6-42% in both AD systems resulted in decreasing of methane yield. The L-AD system has 2-3 times higher volumetric methane productivity than the SS-AD system. The electricity production from 1-tonne a mixture of POME and sewage chemical sludge or sewage biological sludge would be 218 MJ or 60 kWh of electricity. Anaerobic co-digestion POME with sewage sludge has great potential for biogas production.

A novel thermotolerant caproic acid-producing bacterial strain, Clostridium M1NH, was successfully isolated from sewage sludge. Ethanol and acetic acid at a molar ratio of 4:1 proved to be the optimal substrates, yielding a maximum caproic acid production of 3.5 g/L. Clostridium M1NH exhibited remarkable tolerance to high concentrations of ethanol (up to 5% v/v), acetic acid (up to 5% w/v), and caproic acid (up to 2% w/v). The strain also demonstrated a wide pH tolerance range (pH 5.5-7.5) and an elevated temperature optimum between 35 and 40 °C. Phylogenetic analysis based on 16S rRNA gene sequences revealed that Clostridium M1NH shares a 98% similarity with Clostridium luticellarii DSM 29923 T. The robustness of strain M1NH and its efficient caproic acid production from low-cost substrates highlight its potential for sustainable bio-based chemical production. The maximum caproic acid yield achieved by Clostridium M1NH was 1.6-fold higher than that reported for C. kluyveri under similar fermentation conditions. This study opens new avenues for valorizing waste streams and advancing a circular economy model in the chemical industry.

Oil palm empty fruit bunches (EFB) and palm oil decanter cake (DC) were used to investigate biogas production by using solid-state anaerobic co-digestion (SS-AcoD) with 15% total solid (TS) content. Solid state anaerobic digestion (SS-AD) using substrate to inoculum (S:I) ratio of 3:1, methane yields of 353.0 mL-CH4/g-VS and 101.5 mL-CH4/g-VS were respectively achieved from mono-digestion of EFB without oil palm ash (OPA) addition and of DC with 10% OPA addition under mesophilic conditions 35 °C. By adding 5% OPA to SS-AD using 3:1 S:I ratio under thermophilic conditions (55 °C), mono-digestion of EFB and DC provided methane yields of 365.0 and 160.3 mL-CH4/g-VS, respectively. Furthermore, SS-AcoD of EFB:DC at 1:1 mixing ratio (volatile solid, VS basis), corresponding to carbon to nitrogen (C:N) ratio of 32, gathering with S:I ratio of 3:1 and 5% ash addition, synergistic effect is observed together with similar methane yields of 414.4 and 399.3 mL-CH4/g-VS, achieved under 35 °C and 55 °C, respectively. According to first order kinetic analysis under synergistic condition, methane production rate from thermophilic operation is 5 times higher than that from mesophilic operation. Therefore, SS-AcoD could be potentially beneficial to generate biogas from EFB and DC.